I. Field of the Invention
This invention relates generally to electronic display devices, and more particularly to electronic display devices used with sonar equipment such as a “fish finder.”
II. Discussion of the Prior Art
For many years, sonar devices have been used to observe and display the locations and characteristics of objects found underwater. Many of these devices operated using similar components to accomplish this task. Generally in a modern sonar device, a transducer transmits sound waves through the water and detects return echoes of those sound waves. The transducer is connected to a microprocessor via both a transmitter and a receiver. The microprocessor controls the transmission of sound waves via the transmitter and transducer and processes signals received by the microprocessor via the transducer and receiver. More specifically, the microprocessor begins the operation by sending a command to a transmitter to generate a sound wave. The transmitter thereafter sends a sound wave into the water via the transducer. If, as the sound wave travels through the water, it encounters an object the sound wave will bounce off the object creating an echo return. The transducer detects the redirected sound waves (i.e. the echo return) and cooperates with the receiver to forward a signal representative of the echo return to the microprocessor.
The microprocessor is able to calculate the depth of the object detected because the time the sound wave was sent, the time the echo was detected, and the speed sound waves travel through the water are all available to the microprocessor. The microprocessor can also assess the features of the echo returns to determine the size (a.k.a. density) of the object detected. Once the microprocessor has made the required calculations, the microprocessor can use these calculations to control a display.
Displays of various forms have been used in sonar devices. Prior art displays were often mechanically complicated or consumed substantial power making them less than desirable for use when the power source for the sonar and display was a battery. Use of a battery as a power source is common when fishing from a boat without the engine running or when ice fishing. One type of mechanical display involves a motor rotating an arm along which a plurality of light sources are mounted. A series of brushes are used to create electrical connections between the light sources and the microprocessor as the motor turns the arm. Unfortunately, the use of brushes and contacts often proves to be unreliable and such displays frequently do not accurately depict the information received from the sonar. This is particularly true given the often harsh environments in which these components and electronics are often required to operate.
CRTs, liquid crystal and plasma displays are also available, but these generally, consume significant power. They also tend to be too expensive to use when manufacturing a portable, battery operated fish finder.
Therefore, an electronic display device is needed for displaying sonar results that is accurate, simple, inexpensive, power-conserving and which overcomes the problems experienced in past methods and display devices used in sonar applications.